The present invention relates to railroad track-lining devices and methods, and more particularly to such devices and methods using computer modeling to fit an "ideal" curve to existing track position data.
Railroad tracks are laid out according to a mathematical model. All track is comprised of three types interconnected to define a desired path. These types are referred to as tangent, spiral, and curve. Tangent segments are straight or linear; curved segments have a fixed radius; and spiral segments interconnect tangent and curve sections. The point at which spiral segments meet tangent or curve sections are referred to as track transition points. Knowing the location of the transition points and the radius of the curve sections, the spiral sections can be mathematically calculated according to well-known formulas.
The tracks are supported by a flexible bed of ballast and therefore shift from the mathematical model over time. The tracks must therefore be "lined" using a linear or similar apparatus. Track ordinate information is acquired to determine the existing position of the track. The ordinate information is graphed; and an attempt is made to reconstruct the mathematical model for the track based upon the graphed information. After the model is determined, the liner is operated over the track to laterally shift the track as necessary back to the mathematical model.
Automatic track-lining systems have been developed to line railroad track and return the track to an "ideal" configuration. One such system has been manufactured and sold by Jackson Jordan, Inc. of Ludington, Mich., the assignee of the present application as its Model No. ACCL. This liner is disclosed in Canadian Patent No. 1,199,114 issued Jan. 7, 1986 to Bradshaw et al, entitled TRACK CURVE LINING METHOD AND APPARATUS, and assigned to Jackson Jordan, Inc.--the assignee of the present application. The apparatus described therein makes two passes over a length of track to be relined. On the first pass, a light/mask/sensor system collects ordinate information at discrete positions. An on-board computer then calculates a better-fit curve based on the actual data. On the second pass, the liner lines the track in response to the calculated curve information.
The Model ACCL curve liner calculated the model track configuration by manipulating the track data using a digital computer. First, the data was scanned for sequences of relatively constant ordinate values indicating tangent and curve segments of the track. Second, the computer found a "best-fit" line in each spiral area (i.e. those areas between segments of constant ordinate value). Third, the intersections between sloped spiral lines and constant tangent and curve lines were determined and assumed to be the track transition points. Based upon the constant ordinate values and the locations of the transition points, the computer then calculated desired track locations to fit the "ideal" mathematical configuration according to well-known formulas.
Although constituting a significant advance in the track-lining art, Jackson Jordan has continually strived to improve the performance of its equipment. It was noted by Jackson Jordan that the curves determined by prior lining systems were indeed somewhat worse in certain regards than the original curves. Consequently, in certain situations the track was being moved away from the ideal mathematical curve; and system operators had to compensate for the erroneous computer calculation to empirically produce an ideal curve which appeared "right". Consequently, the computer calculation of the curve required significant human interaction and therefore possible operator error.